Mutation mutation = new Mutation(Keyspace.SYSTEM_KS, SystemKeyspace.getSchemaKSKey(ksName));
ColumnFamily cf = mutation.addOrGet(SchemaColumnFamiliesCf);
int ldt = (int) (System.currentTimeMillis() / 1000);
Composite prefix = SchemaColumnFamiliesCf.comparator.make(cfName);
cf.addAtom(new RangeTombstone(prefix, prefix.end(), timestamp, ldt));
for (ColumnDefinition cd : allColumns())
cd.deleteFromSchema(mutation, timestamp);
for (TriggerDefinition td : triggers.values())